This invention is an improvement in applicant's U.S. Pat. No. 3,745,207 for the recovery of waste pickle liquor. The reactor in that patent operated at a temperature above 800.degree. C. (or 1500.degree. F.) and readily caked up, thus requiring frequent shut-downs for cleaning in spite of the fact that its inclined bed for particles was vibrated. Furthermore, the system of that patent required a relatively large amount of fuel, not only for the reactor but also in order to concentrate the waste liquor before being introduced into the reactor. The resulting iron oxide product was of low grade and could be used only for feed to a blast furnace. Furthermore, the exhaust gases from the system required much more scrubbing to be non-polluting, and the apparatus required expensive acid resistant equipment, particularly to withstand the higher temperatures involved in the system.
Other prior art systems such as the oxygen lance or Oceanic Process did not produce a complete reaction, and much sludge was formed requiring additional washing up operations and disposal recycle problems.
The Wean-Pori System, although it operated at a lower temperature than applicant's prior patent system, required operation under pressure and involved many and severe maintenance problems, particularly because of the corrosive materials being processed.
The Lurgi Chemi Fluidized Bed Process system had severe caking problems and was far from economical on fuel.
The Spray Roaster or Woodall Dunckham System also operated at high temperatures, had difficulty with clogging of the spraying nozzles, involved high maintenance problems and high fuel costs.
Both the Lurgi and Spray Roaster systems are large and bulky and require a large capital cost.